Former European 400m hurdles champion Rhys Williams feels he should not have been suspended for having a banned substance in his system due to a contaminated supplement.

Williams and fellow Welshman Gareth Warburton were “at fault or negligent” in failing to check supplements they took in an energy drink which contained banned substances, according to a UK Anti-Doping (UKAD) official report which was published on Monday.

The pair failed drugs tests last summer - forcing the athletes to miss both the Commonwealth Games and the European Championships. Although their bans were reduced as it was accepted they did not knowingly use banned substances, Williams, 30, received a suspension of four months with Warburton, 31, banned for six months.

Both athletes are now clear to compete again after admitting their careers would have been over had the maximum four-year ban for serious cases of intentional doping been handed out, but Williams - who won European 400m hurdles gold at Helsinki in 2012 - still feels he has done nothing wrong.

“I have to accept what the suspension is but if you ask me I shouldn’t have had one,” said Williams.

“They found something in my body that was a nanogram amount of a veterinary substance which stays in your body for nine months, so it was definitely not something a 400 metre hurdler would take to get a performance.

“It’s all bizarre and it’s impossible to foresee a small amount in a supplement that’s got labelling.

“I think I’ve already served more than enough punishment by missing the Commonwealth Games and the European Championships.

“But I’m relieved now I can compete this season because I thought it could be the end of my athletics career, even though I’d done nothing wrong.”